In healthcare packaging, even well-designed systems can encounter unexpected challenges when exposed to real-world processing conditions. Seal integrity, for example, is not only a function of materials and sealing parameters; it is also impacted by other factors such as sterilization. When issues arise, testing becomes essential to understand what is truly happening at the seal interface.
In this blog, I will work through a recent case study to share with you how we approach packaging concerns, identify root causes, and work with customers to resolve the issue. In this case, a customer approached me with concerns about seal performance in their ready-to-use cartridge packaging. The issue was clearly defined: seals met all specifications after production, but during visual inspection after sterilization the packaging showed signs of seal creep. After checking validation data, it was confirmed that the sealing process itself was robust. This pointed to an external, process-related stressor during sterilization as the likely cause, rather than a deficiency in sealing parameters.
Before determining the root cause of the seal creep, I needed to investigate first whether the observed seal creep represented an actual loss of package integrity or simply a cosmetic change caused by process stresses. To clarify, seal creep is the partial separation or movement of a seal caused by unwanted stresses applied to that area. Technically, seal creep is not always a failure or an integrity breach; the concern is that it could be a failure or turn into one, that is why it is important to always investigate seal creep.
To investigate seal creep, I selected dye penetration testing in accordance with ASTM F1929. This method provides a direct visual indication of channel leaks within the seal. However, distinguishing true leaks from dye wicking is critical. Because Dupont Tyvek® is naturally porous, prolonged dye exposure can lead to migration into the material, creating false-positive results. To address this, strict adherence to ASTM F1929 exposure timing needs to be maintained. True channel leaks appear rapidly, typically within the first five seconds, while slower dye movement is generally due to wicking. By combining controlled dye testing with visual inspection and peel test data, it was confirmed that the seal creep, in this case, did not represent a loss of integrity.
With integrity verified, the investigation shifted to understanding the root cause of the visual seal creep after sterilization. Although not a failure in this case, it remained important to find the root cause to prevent recurrence and reduce future risk.
Since the seal creep occurred after sterilization, we decided to investigate the steam sterilization process. Steam sterilization cycles create dynamic pressure differentials throughout the package. When combined with the permeability characteristics of DuPont Tyvek® lids, these pressure changes can generate significant mechanical stress at the seal interface. Through controlled testing, I demonstrated that excessive pressure build up within the package during the sterilization cycle was contributing to the observed seal creep. Working closely with the customer, adjustments to the sterilization profile were validated, and alternative configurations with improved permeability were evaluated. Follow-up testing confirmed that these changes reduced stress on the seal and prevented the seal creep.
This case highlights the importance of testing the full packaging system and process, when evaluating seal integrity. Initial validation alone is not sufficient; performance must be assessed under actual processing conditions. As seal integrity depends on the interaction between sterilization parameters, material properties, and overall package design. A thorough understanding of DuPont Tyvek® and coating behavior, supported by appropriate testing methodologies, is fundamental to both successful development and effective troubleshooting of primary packaging systems.
